• Restorative Dentistry and Endodontics
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• 제11권1호
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• pp.43-52
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• 1985

The purpose of this study was to measure the Micro-Knoop Hardness of three commercial visible light-cured composite resins (Plurafil-super, He1iosit and Durafi) according to the difference of depth and shade. Specimens of the resin were prepapared in plastic tubes 5mm in diameter with height of 5mm, and the tubes were put into the columned holes in stone molds. The molds were exposed to the visible light through the hole 5mm in diameter in metal plate. Specimens were sectioned (longitudinally) with disk. Knoop Hardness measurements were made at the depth of surface, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0mm from the surface to the deep portion. Knoop Hardness numbers were taken on each depth under 20gm load for 10 seconds with Shimadzu Tester. The following results were: 1. The highest hardness value was measured at 0.5mm depth. Then the deeper the depth, the lesser the hardness was observed. 2. The value of hardness was directly propotional to the time of exposure to the light. 3. The hardness of light shade resin was higher than the that of the dark shade. 4. The pattern of hardness change at varying depth is similar to all the experimental materials with no relation to the shade nor exposure time.

• Restorative Dentistry and Endodontics
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• 제14권1호
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• pp.179-188
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• 1989

The purpose of this study was to measure Micro vicker's hardness of 4 kinds of anterior Composite resins (Pyrofil light bond anterior, Lite-fil anterior, Photo clear fil anterior, Silux) and 6 kinds of posterior Composite resin (Pyrofil light bond posterior. Lite-fil posterior, Photo clear fil posterior, Occlusin posterior, Palfique light posterior, P-30, posterior) according to deference of depth and distance of light tip from surface of composite resin. Each composite resin was filled into Teflon tube of 5mm in diameter and 5mm in depth, celluloid matrix was covered and the light in accordance with each composite resin was irradiated in distance of zero millimeter and 1 cm from light tip to surface of composite resin for 30 seconds. Specimens were sectioned longitudinally with cutting device. Microvicker's hardness measurements ware made at the depth of surface, 1mm, 2mm, 3mm, 4mm and 5mm from the surface to deep portion. Vicker's hardness numbers were taken on each depth under 200gm load for 30 seconds with MVK-E. The following results were: 1. The highest hardness value was measured at 1 mm depth. Then the deeper the depth, the lesser the hardness was observed. 2. The hardness value of anterior composite resins is lower than one of posterior composite resins. 3. Hardness number of composite resin irradiated in distance of zero millimeter from surface of composite resin was higher than one of 1 cm from surface of composite resin. 4. The pattern of hardness change at varying depth was similar to all the experimental material with no relation to distance of light from specimen.

• Tribology and Lubricants
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• 제32권1호
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• pp.18-23
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• 2016

The effective case depth for case-hardened rolling bearing has been discussed. For this purpose, rolling contact fatigue tests for ball bearings built with inner race of various hardness values were conducted until L₁₀ calculating rating life using a bearing life test machine under radial loading. Then, the distribution of residual stress below the inner raceway, which depended on the hardness value, was measured by X-ray diffraction. As a result, the linear relationship was established between the hardness value of the inner race and the theoretical shear stress evaluated at the depth where the residual stress disappeared below the inner raceway. Based on the relationship, it could be found that the factor of safety in bearing manufacturer’s rules for the effective case depth of case hardened rolling bearings was set higher. However, it could be also found that the hardness values at the depth where the maximum shearing stress acted below the raceway surface in a tapered roller bearing hardened by the carburizing process, were not sufficient for preventing plastic deformation under the basic dynamic load rating. Consequently, further efforts were still required to reduce or to disperse the contact load on the material design of a rolling bearing in order to prolong its life.

• Journal of Biosystems Engineering
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• 제23권4호
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• pp.351-358
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• 1998

It was intended to investigate that how hardness of chestnut shell affects the flame peeling characteristics of Korean Chestnut. Effects of the hardness on the flame peeling characteristics need to be found to establish the optimum drying conditions for chestnut of various cultivars, sizes and harvested years. The equation based on the hardness of the chestnut shells was developed. It was found that the flame peeling characteristics of the corresponding to the various drying conditions did not differ significantly to the groups with the same hardness. The flame peeling characteristics of the chestnut with the same hardness were not influenced by cultivars, size, and harvested year, The peeling ratio and the heating depth were increased by decrease of the hardness of the chestnut shells. On the other hand, the peeling ratio and the heating depth were increased as the flame temperature was increased with the same hardness. When the heating depth was limited to 2.1 mm regarding the process characteristics and the damage ratio, the proper hardness and peeling ratio of chestnut shells were 1,369.8 g/$\textrm{mm}^2$ and 83.9%, respectively, at the flame temperature of $700^{\circ}C$. And also 1,517.7 g/$\textrm{mm}^2$ and 80.7% at 75$0^{\circ}C$.

• 대한기계학회논문집A
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• 제28권5호
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• pp.578-585
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• 2004

Hardness test is performed for determination of the other properties, such as strength, wear resistance and deformation resistance, as well as hardness itself. And it is performed for prediction of residual lifetime by analysis of hardness reduction or hardness ratio. However, hardness test has limitation that observation of residual indent is needed for determination of hardness value, and that is the reason for not to be widely used in industrial field. Therefore, in this study, we performed researches to obtain Brinell hardness value from quantitative numerical formula by analysing relationship between indentation depths from indentation load-depth curve and mechanical properties such as work hardening exponent, yield strength and elastic modulus.

• 한국재료학회지
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• 제13권9호
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• pp.606-612
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• 2003

Surface and mechanical properties of thin films with submicron thickness was characterized by nanoindentation with Berkovich and Vickers tips, and scanning probe microscopy. Nanoindention was made in a depth range of 15 to 200 nm from the surface by applying tiny force in a range from 150 to $9,000 \mu$N. Stiffness, contact area, hardness, and elastic modulus were determined from the force-displacement curve obtained. Reliability was first tested by using fused quartz, a standard sample. Elastic modulus and hardness values of fused quartz measured were the same as those reported in the literature within two percent of error. Mechanical properties of ITO thin film were characterized in a depth range of 15∼200nm. As indentation depth increased, elastic modulus and hardness decreased by substrate effect. Ion beam deposited DLC thin films were indented in a depth range of 40∼50 nm. The results showed that the DLC thin film using benzene and bias voltage 0∼-50 V has elastic modulus and hardness value of 132 and 18 GPa respectively. Pure DLC thin films showed roughnesses lower than 0.25 nm, but silicon-added DLC thin films showed much higher roughness values, and the wavy surface morphology.

• 한국산업융합학회 논문집
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• 제27권1호
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• pp.1-7
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• 2024

This study was investigated the effect of heat treatment on the microstructure and hardness of internally hardened ductile cast iron roll. The following conclusions were obtained. Some of the graphite was decreased and a bainite was produced by heat treatment. It decreased due to the decomposition of some of the cementite precipitated in the as-cast by heat treatment, but there was no significant change when it reached a certain depth. Hardness increased due to formation of bainite by heat treatment. On the surface, the hardness decreased due to the decrease in the amount of transformation of cementite into bainite, but there was no change beyond a certain depth.

• 한국약용작물학회지
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• 제19권4호
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• pp.246-250
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• 2011

This study was carried out to investigate the characteristics of Rhizome rot incidence of Platycodon grandiflorus by cultivation period and ridge width and furrow depth. The three types of ridge width 0.8, 1.0, and 1.2 m and several levels of furrow depth and 6 levels cultivation period. This experiment was done in farmer's farm and the treatments were also classified in the same spot. In this investigation, ridge width, soil water content, soil hardness, and cultivation period were positively related with Rhizome rot incidence, however, furrow depth was negatively related with that. So this experiment could draw a conclusion : excess water damage and soil hardness could directly or indirectly effect on the Rhizome rot incidence, so cultivation method should be developed such as making underground ditch or cultivation in well draining soil for escaping excess waster damage.

• 대한기계학회논문집
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• 제7권1호
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• pp.19-27
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• 1983

This paper deals with hardness and wear characteristics of ion-nitrided metal, and with ion-nitride processing which is concerned with the effects of added carbon content in gas atmosphere. A small optimal amount of carbon content in gas atmosphere increase compound layer thickness, as well as to increase diffusion layer thickness and hardness, and reduces wear rate when the applied wear load is small. It is found in the analysis that under small applied wear load, the critical depth where voids and cracks may be created and propagated is located at the compound layer, so that the abrasive wear where hardness is an important factor, is created and the existence of compound layer reduces the amount of wear. When the load becomes large, the critical depth is located below nucleation and propagation, is created and the existence of compound layer increase wear rate.

• 한국표면공학회지
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• 제46권1호
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• pp.48-53
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• 2013

In the present work, it was investigated a behavior of hydrogen embrittlement at the subsurface zones of 590 DP steels by using the micro-Vickers hardness test. The micro-Vickers hardnessess of DP steels were measured to evaluate the degree of embrittlement as the effective hardening depths of subsurface zones with hydrogen charging conditions. The results showed that the distributions of micro-Vickers hardness in width varied from maximum hardness 239.5 Hv to minimum hardness 174 Hv, while the depth of effective hardening layer at the subsurface zones of DP steels was from $320{\mu}m$ to $460{\mu}m$ with hydrogen charging conditions, respectively. It was proposed that the distribution of microhardness be used as the evaluation index of the degree of embrittlement. But the variations of martensite volume fractions were not affected along depth of hardening at the same changing time, hydrogen charging times were appeared as an effective factor of the degree of embrittlement. Therefore, the micro-Vickers hardness test is an attractive tool for evaluation of hydrogen embrittlement at the subsurface zones of these DP steels.